Rendering is a process that generally converts animal products into more useful materials. Rendering typically separates the fat from the bone and protein and yields a fat commodity (such as grease) and a protein meal (meat or bone meal). Batch cooking systems and continuous cooker systems have been used for rendering. While these systems may be helpful in rendering, there are deficiencies that can lead to less than desirable end products and also can be energy intensive and are expensive to operate.